Note: Descriptions are shown in the official language in which they were submitted.
I
A lifting wall arrangement and a segment of a lifting wall arrangement
TECHNICAL FIELD
The present invention relates to a lifting wall arrangement at an end wall of
a drum mill. The
invention further relates to a segment of a lifting wall arrangement and a
drum mill comprising a
lifting wall arrangement.
BACKGROUND
In a rotating drum mill material in the form of crushed ore is fed into one
end of the mill, the input
end wall, and milled ore is extracted through a centrally positioned material
output tap at the
second end of the mill, the output end wall. In materials processing a grinder
is a machine for
producing particle size reduction through attrition and compressive forces at
the grain size level.
Atypical type of fine grinder is the drum mill. Water is supplied during the
milling such that finely
divided ore particles and water form a pulp or slurry. The drum mill typically
comprises a shell
forming a large, principally cylindrical, compartment located between the
input end wall and the
output end wall. This compartment is generally known as the grinding chamber.
In association
with the output end wall a lifting wall arrangement is arranged for the
discharge of pulp from the
grinding chamber. The lifting wall arrangement comprises a plurality of pulp
lifters, wherein each
pulp lifter generally comprises an inner wall facing the grinding chamber and
an opposing outer
wall facing the output end wall. The pulp lifters are arranged radially in
relation to the rotation
axis and rotate with the mill. A lifting wall arrangement may comprise
radially inner pulp lifters
and radially outer pulp lifters. A number of radially arranged limiting walls
or carriers are
provided on the inner or the outer wall, evenly distributed around the
rotation axis. Said carriers
define a number of compartments, known as pulp lifting chambers, together with
the inner wall
and the outer wall. The pulp lifting chambers typically become narrower in the
direction towards
the centre of rotation where the pulp is lead to a central discharge cone. The
discharge cone
extends into the output tap. The inner wall of a pulp lifter typically
comprises sieving openings
through which the pulp or slurry is entering the pulp lifting chamber. During
rotation of the mill,
the pulp in the grinding chamber is
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thus led through the sieving openings, into the pulp lifting chambers when the
pulp
lifter is positioned at a lower position of the rotation. When the pulp lifter
has reached
an upper position of the rotation, the pulp falls down towards the discharge
cone and
thus the output tap. The pulp lifting chambers thus form a number of discharge
chan-
nels whose task it is to lead the mineral-containing pulp out from the
grinding chamber
of the mill during rotation of the mill. As used herein the term pulp also
includes slurry,
as well as other materials being ground.
A common problem with lifting wall arrangements of today is the installation
and re-
moval of the separate components. The outer wall of each pulp lifter is
typically first
arranged on a correct position and attached to the output end wall of the mill
by bolts
from the inside of the mill. The inner wall is subsequently attached to the
outer wall by
long bolts extending through the inner wall and the outer wall. This procedure
is cum-
bersome and time consuming. It should also be pointed out that the long bolts
are
heavy and awkward to handle by an operator during assembly and disassembly
work.
Document WO 2011/095692 Al for examples discloses a pulp lifter assembly for a
rotary grinding mill where a grate is attached to each pulp lifter with
fasteners.
Document US 3799458 A discloses a tube mill material lifting wall comprising
two
discs each being composed of individual segments, wherein opposing segments
are
joined at their outer ends and has lifting blades there between adapted to
lift the mate-
rial being treated within the drum as it rotates. The opposing segments are
connected
in pairs by a connecting web affixed to the casing of the tube mill to form a
member
with a U-cross-section. The segments are thus welded to their connecting web
so that
they form a rigid unit. The web is screwed to the tube mill casing. The
segments are
also fixedly joined by spacer elements. This is a complex construction which
will result
in a time consuming and inconvenient installation and maintenance of the compo-
nents of the lifting wall.
Various constructions of lifting wall arrangements thus exist but there is
still a need to
develop a lifting wall arrangement, which reduces the time for
installation/removal of
various components and which optimises the weight of the lifting wall
arrangement.
SUMMARY OF THE INVENTION
3
An object of the present invention is to achieve a lifting wall arrangement
which results in
improved handling, installation and maintenance service.
Another object of the invention is to achieve a lifting wall arrangement which
is suitable for
automated installation.
A further object of the invention is to achieve a lifting wall arrangement
with an optimized weight.
A further object of the present invention is to achieve a segment of a lifting
wall arrangement
which results in improved handling, installation and maintenance service.
Another object of the invention is to achieve a drum mill which results in
cost-effective handling,
installation and maintenance service.
The herein mentioned objects are achieved by a lifting wall arrangement, a
segment of a lifting
wall arrangement and a drum mill.
According to an aspect of the invention a lifting wall arrangement at an end
wall of a drum mill is
provided. The lifting wall arrangement has a plurality of segments which are
removably
installable on the end wall, wherein each segment comprises an inner wall and
an opposing
.. outer wall, wherein at least one lifting blade is arranged on said outer
wall, such that the outer
wall, the lifting blade and the inner wall define a discharge channel leading
to a central
discharge cone, and wherein said inner wall forms a part of a sieving wall
facing a grinding
chamber in the drum mill, wherein each segment constitutes an integrated unit
adapted to be
installed on the end wall. By designing each segment of the lifting wall
arrangement as
individual integrated units the installation and the removal of the segment is
facilitated. Since the
segment is a one-piece unit the amount of fasteners needed to attach the
segment to the end
wall is reduced. Instead of first attaching the outer wall to the end wall and
subsequently
attaching the inner wall to the outer wall as in common lifting wall
arrangements, the inner wall
and the outer wall are manufactured as one integrated unit and are thus
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connected prior to mounting on the end wall. This way, both components are
preas-
sembled into a one piece unit that can be immediately installed on the end
wall.
Hence, the number of fasteners needed can be reduced. Also, since the long
bolts
used to attach the inner wall to the outer wall are avoided, the weight of the
lifting wall
arrangement is optimised. A lifting wall arrangement is thereby achieved,
which re-
sults in improved handling, installation and maintenance service and
facilitates as-
sembly and disassembly work.
The lifting wall arrangement is essentially configured as a circular disk or
plate. The
segments are radially arranged in relation to the rotation axis of the drum
mill. The
segments are thus typically configured as sectors of a circle
circumferentially sur-
rounding the central discharge cone. The lifting wall arrangement comprises at
least
one circle of interconnected segments or suitably two interconnected segments
ar-
ranged as an outer circle and an inner circle. The outer segments are thus
arranged
radially on the outside of the inner segments and thereby closer to the
periphery of the
lifting wall arrangement. The lifting wall arrangement may alternatively
comprise outer
segments, intermediate segments and inner segments. The segments of the
lifting
wall arrangement may be arcuate or curved. The segments may alternatively have
a
semi-curved, a dogleg or any other known configuration.
The integrated unit is preferably adapted to be attached to the end wall from
the out-
side of the drum mill. The integrated unit is suitably adapted to be attached
to the end
wall only from the outside of the drum mill. This further facilitates the
installation and
removal of the individual segments and the lifting wall arrangement may
thereby be
suitable for automated installation. The individual segments may thereby be in-
stalled/removed by means of a robot provided with a lift arm or similar
handling device.
To facilitate handling, the segment inner wall of the integrated unit may be
equipped
with lifting eyes. In this way, the installation procedure may be streamlined
and there-
by simplified.
The integrated unit suitably comprises first mounting means adapted to,
through
mounting holes in the end wall, interact with complementary second mounting
means
installable from the outside of the drum mill. The first mounting means
preferably
comprises a fastener body insert arranged in a recess in the wall of the
integrated unit
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facing the end wall. The fastener body insert suitably constitutes a threaded
bushing
or sleeve which can be tubular. The first mounting means is thus arranged in a
recess
in the outer wall of the segment such that the first mounting means is facing
the
mounting hole. The second mounting means may thereby be installed from the out-
5 side of the drum mill such that it interacts with the first mounting
means. In the case
where the first mounting means is a threaded bushing or similar the second
mounting
means suitably constitutes a threaded bolt or similar. Since the segment is an
inte-
grated unit the number of fixing points can be reduced and the allocation of
fixing
points can be limited to the outer wall. This way, a rigid and resistant
construction is
achieved.
The first mounting means may comprise a guide member projecting from the
recess,
wherein the guide member is adapted to guide the integrated unit to a correct
position
against the end wall by interaction with the mounting holes.
The inner wall of the integrated unit preferably comprises sieving openings.
In the
case where the lifting wall arrangement comprises several circles of segments,
the
outer segments suitably comprise inner walls with sieving openings whereas the
in-
termediate and/or inner segments comprise inner walls without sieving
openings. A
front wall comprising sieving openings is suitably called a grate. A front
wall not com-
prising sieving openings is suitably called a blind grate. The segments with
sieving
openings are suitably arranged along the periphery of the lifting wall
arrangement
such that when the segment is in a bottom position during rotation of the
mill, grinded
material (pulp) will enter through the sieving openings into the discharge
channel of
the segment. As the lifting wall arrangement rotates and the segment reaches a
top
position, the pulp will fall through the discharge channels in the inner
segments to the
central discharge cone. The lifting wall arrangement thus constitutes a
discharge sys-
tem for the drum mill.
The inner wall and the outer wall of the segment are can be connected by
vulcanizing
and thereby form an integrated unit. The segment can alternatively be formed
as an
integrated unit by chemical bonding or mechanical connection. Vulcanizing or
casting
are conceivable methods.
6
The segments may comprise polymer and/or metal and/or a ceramic material. The
segments
may comprise a compound. By forming the segments as integrated units of
polymer materials, a
light-weight lifting wall arrangement is achieved. The segments may comprise
steel, or any wear
or abrasive resistant materials such as Cr-Mo steels, white cast iron or any
other known
material having desired properties.
In one aspect, there is provided a lifting wall arrangement at an end wall of
a drum mill, having a
plurality of segments which are removably installable on the end wall, wherein
each segment
comprises an inner wall and an opposing outer wall, wherein at least one
lifting blade is
arranged on the outer wall, such that the outer wall, the lifting blade and
the inner wall define a
discharge channel leading to a discharge cone, and wherein the inner wall
forms a part of a
sieving wall in the drum mill, and wherein each segment constitutes an
integrated unit adapted
to be installed on the end wall, wherein the integrated unit is adapted to be
attached to the end
wall from an outside of the drum mill, wherein the integrated unit comprises
first mounting
means adapted to, through mounting holes in the end wall, interact with
complementary second
mounting means installed from the outside of the drum mill, and wherein the
first mounting
means comprises a fastener body insert arranged in a recess or a bore in the
outer wall of the
integrated unit facing the end wall.
In another aspect, there is provided a segment of a lifting wall arrangement
at an end wall of a
drum mill, wherein the segment is removably installable on the end wall,
wherein the segment
comprises an inner wall and an opposing outer wall, wherein at least one
lifting blade is
arranged on the outer wall, such that the outer wall, the lifting blade and
the inner wall define a
discharge channel leading to a discharge cone, and wherein the inner wall
forms a part of a
sieving wall in the drum mill, the segment constitutes an integrated unit
adapted to be installed
on the end wall wherein the segment is adapted to be attached to the end wall
from an outside
of the drum mill wherein the integrated unit comprises first mounting means
adapted to, through
mounting holes in the end wall, interact with complementary second mounting
means installed
from the outside of the drum mill, and wherein the first mounting means
comprises a fastener
body insert arranged in a recess or a bore in the outer wall of the integrated
unit facing the end
wall.
In another aspect, there is provided a drum mill, wherein the drum mill
comprises the lifting wall
arrangement, the lifting wall arrangement having the plurality of segments
which are removably
installable on the end wall.
Date Recue/Date Received 2023-06-22
6a
The term lifting blade refers to any known mean such as blade, ribs or vanes
which functions to
lift any pulp which has left the grinding chamber through sieving opening or
grids in a lifting wall
and will deposit such pulp on a discharge cone.
Further objects, advantages and novel features of the present invention will
become apparent to
one skilled in the art from the following details, and also by putting the
invention into practice.
Whereas the invention is described below, it should be noted that it is not
restricted to the
specific details described. Specialists having access to the teachings herein
will recognise
further applications, modifications and incorporations within other fields,
which are within the
scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
For fuller understanding of the present invention and further objects and
advantages of it, the
detailed description set out below should be read together with the
accompanying drawings, in
which the same reference notations denote similar items in the various
diagrams, and in which:
Figure 1 schematically illustrates a drum mill comprising a lifting wall
arrangement
according to an embodiment of the invention;
Date Recue/Date Received 2022-11-29
7
Figure 2 schematically illustrates a lifting wall arrangement according
to an embodiment of
the invention;
Figure 3a-f schematically illustrates segments of a lifting wall arrangement
according to
various embodiments of the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 shows a part of a drum mill comprising a lifting wall arrangement
according to an
embodiment of the invention. The drum mill comprises a mill shell 1 and two
end walls, an input
end wall (not shown) and a discharge end wall 2. The mill shell 1 and the end
walls 2 form a
substantially cylindrical compartment called the grinding chamber 3. The drum
mill rotates
around a rotation axis A. The mill shell 1 is internally lined with a lining 4
of some wear-resistant
material, for example an elastomer. A discharge trunnion 5 extends centrally
from the discharge
end wall 2. Inside the drum mill, at the discharge end wall 2, a rotating
lifting wall arrangement 8
is provided. The lifting wall arrangement 8 is adapted to lift the grinded
material inside the
grinding chamber and lead it out of the drum mill through the discharge
trunnion 5. The lifting wall
arrangement 8 comprises a central discharge cone 9 and a plurality of segments
10 radially
arranged circumferentially surrounding the discharge cone 9. The segments 10
are attached to
the end wall 2 and the central discharge cone 9 is arranged in fluid
communication with the
discharge trunnion 5. The segments 10 may also be called pulp lifters. The
lifting wall
arrangement 8 is further described in figure 2.
Figure 2 shows a cut section of a lifting wall arrangement 8 according to an
embodiment of the
invention. The lifting wall arrangement 8 is installed at an end wall 2 of the
drum mill as
described in figure 1. The lifting wall arrangement 8 has a plurality of
segments 10 which are
removably installable on the end wall. The segments are designed as sections
of a circle and
together form a circle, circumferentially surrounding the central discharge
cone 9 of the lifting
wall arrangement 8. According to this embodiment, segments 10 (FIG. 1), and
thus the lifting
wall arrangement 8 comprises an outer circle of segments 10A, an intermediate
circle of
segments 10B and an inner circle of segments 10C. The circles of segments 10A,
10B, 10C and
the discharge cone 9 together form a circular disk. Each of segments 10
comprises an inner
wall 10:1 and an opposing outer wall 10:2, wherein at least one lifting blade
11 is arranged on
said outer wall 10:2, such that the outer wall, the lifting blade and the
inner wall define a
discharge channel 12 leading to the central discharge cone 9. The segment
outer wall 10:2 is
Date Recue/Date Received 2022-11-29
8
abutting the end wall 2 of the drum mill and the segment inner wall 10:1 forms
a part of a sieving
wall 13 facing the grinding chamber 3 in the drum mill. Each of segments 10
constitutes an
integrated unit adapted to be installed on the end wall 2.
With reference to fig. 1 segments 10 in the outer circle, referred to as outer
segments10A,
comprise sieving openings 14 in the inner wall 10:1. The inner walls 10:1 of
the outer segments
10A thus constitute grates. The inner walls 10:1 of the intermediate segments
10B and the inner
segments 10C are so called blind grates, without sieving openings. When the
outer segments
10A are in a bottom position during rotation of the mill, grinded material
(pulp) will enter through
the sieving openings 14 into the discharge channels 12 of the segments 10A,
10B, 10C. As the
lifting wall arrangement 8 rotates and the outer segments 10A reach a top
position, the pulp will
be lead through the discharge channels 12 in the intermediate 10B and inner
segments 10C to
the central discharge cone 9 and out of the drum mill. Alternatively, segments
10A, 10B, 10C
can comprise sieving openings 14 in the inner wall 10:1.
As shown in the enlargement view in fig. 2 the segments 10 constituting
integrated units are
suitably installed on the end wall 2 by means of first mounting means 20 which
interact with
complementary second mounting means 30 installed from the outside of the drum
mill. The first
mounting means 20 and the second mounting means 30 thus interact through
mounting holes
35 in the end wall 2 of the mill drum.
Figures 3a-3f show exemplary segments 10A, 10B, 10C of a lifting wall
arrangement 8
according to various embodiments of the invention. The exemplary segments 10A,
10B, 10C
are configured as described in relation to figure 2 and thus comprise an inner
wall 10:1 and an
outer wall 10:2 and at least one lifting blade 12 integrated as a one-piece
unit. The segments
may be formed as integrated units by chemical bonding, mechanical connection
or be
configured to achieve a shape-bound connection with one another. Vulcanizing,
casting,
welding, gluing, bolting, riveting or any other known joining methods,
depending on the selected
combination material. The segments may comprise elastic polymers, ceramic
materials,
cemented carbides steel alloys and/or metal or combinations thereof. The
segments may
alternatively comprise a compound from any of the above mentioned materials.
The segments
specifically comprise wear-resistant materials such as a steel alloys suitable
to be used in an
iron ore mill.
Date Recue/Date Received 2022-11-29
9
Figure 3a shows a segment 10A configured as a section of a circle which
comprises three lifting
blades 11. One lifting blade 11a, 11c is radially arranged at each side of the
segment 10 facing
an adjacent segment and one lifting blade 11 b is arranged there between. The
lifting blades 11
are thus arranged such that two discharge channels are formed 12a, 12b. When
two such
segments are arranged adjacent each other, one lifting blade of the first
segment will abut a
lifting blade of the second segment. The inner wall 10:1 comprises sieving
openings 14 for the
entry of grinded material into the discharge channels. The inner wall 10:1 is
thus a grate. The
discharge channels 12 may also be denominated pulp-lifting chambers. The
segment according
to figure 3a is suitably an outer segment 10A adapted to be arranged along the
periphery of the
lifting wall arrangement 8.
Figure 3b shows the outer wall 10:2 of the segment 10A in figure 3a. With
reference also to
the enlargement view in fig. 2 the outer wall 10:2 comprises first mounting
means 20 in the
form of fastener bodies 21 such as holding inserts arranged in recesses or
bores in the outer
wall. The segment 10A is adapted to be positioned such that the fastener
bodies 21 are in
line with mounting holes 35 in the end wall 2. Second mounting means 30 may
thereby be
installed from the outside of the drum mill such that it interacts with the
first mounting means
20. The fastener bodies 21 are suitably threaded bushings or sleeves that can
be tubular.
The second mounting means 30 are suitably threaded bolts 31 or similar means
interacting
with the threaded bushings or sleeves. As shown in the enlargement in fig. 2 a
washer 36
can be placed between the head of the bolt 31. Also a rubber washer 37 can be
arranged
between the washer 36 and the outside of end wall 2 of the drum mill.
Figure 3c shows an arcuate segment 10A comprising two lifting blades 11a, 11c.
The lifting
blades are arranged such that a discharge 12a channel is formed in the middle
of the segment
and such that the segment has open ends towards adjacent segments. This way,
when two
such segments 10A are arranged adjacent each other a discharge channel 12a
will be formed
between the two segments. The inner wall comprises sieving openings 14 for the
entry of
grinded material into the discharge channels 12. The segment 10A according to
figure 3c may
be an outer segment 10A adapted to be arranged along the periphery of the
lifting wall
arrangement 8.
Figure 3d shows an arcuate segment 10C comprising one lifting blade 11a. The
lifting blade ha
is arranged centrally on the segment such that the segment has open ends
towards adjacent
Date Recue/Date Received 2022-11-29
10
segments. This way, when two such segments are arranged adjacent each other a
discharge
12a channel will be formed between the two segments. The segment has an inner
wall 10:1
without sieving openings, a so called blind grate. The segment is suitably an
inner segment 10C
adapted to be arranged in direct connection with the central discharge cone 9
of the lifting wall
arrangement 8. Figure 3e and 3f show segment 10B configured as sections of a
circle
comprising inner walls 10:1 without sieving openings.
Figure 3e shows a segment 10B comprising two lifting blades 11a, 11c. The
lifting blades 11a,
11c are arranged such that a discharge channel 12 is formed in the middle of
the segment and
such that the segment has open ends towards adjacent segments. The segment is
suitably an
intermediate segment 10B. Figure 3f comprises three lifting blades 11a, lib,
11c. One lifting
blade 11a, 11c is arranged at each side of the segment facing an adjacent
segment and one lifting
blade llb is arranged there between. The lifting blades are thus arranged such
that two
discharge 12a, 12b channels are formed. The segment is suitably an
intermediate segment
10B.
The foregoing description of the preferred embodiments of the present
invention is provided for
illustrative and descriptive purposes. It is not intended to be exhaustive or
to restrict the
invention to the variants described. Many modifications and variations will
obviously be
apparent to one skilled in the art. The embodiments have been chosen and
described in order
best to explain the principles of the invention and its practical applications
and hence make it
possible for specialists to understand the invention for various embodiments
and with the
various modifications appropriate to the intended use.
Date Recue/Date Received 2022-11-29
